Getting invoices paid faster, without being unpleasant about it
What actually moves a payment date: when you send, what the subject line says, whether they opened it, and how long you wait before the second email.
Most advice about getting paid is about being firmer. In practice the things that move a payment date are duller than that and almost all of them happen before the invoice is late.
Send it the day the work finishes
An invoice sent a fortnight after the job is an invoice arriving at somebody who has stopped thinking about the job. Net 30 starts when you send, not when you finish, so a fortnight of delay is a fortnight of your own money.
Address a person, not a company
“Hello Norwood Inc” reads as generated, because it is. Somebody in accounts payable is who actually receives it, and a letter addressed to them gets answered where a letter addressed to their employer gets forwarded, if that.
Find out whether they opened it
“Not paid” and “not opened” are different problems with different answers. If an invoice has been sitting unopened for a week, the likeliest explanation is that it never arrived — a new sending domain lands in junk more often than anybody expects — and chasing harder is exactly the wrong response.
Wait a week between nudges
The reply somebody owes you takes a working week to arrive. A second email inside that window reads as impatience rather than as a reminder, and a customer emailed twice in a week starts filtering the sender — which costs you the third email, the one that mattered.
Firmness comes from being unambiguous about the facts. It needs no threat at all.
Never threaten what you have not decided
Late fees you never agreed, interest that is not in your terms, a collections agency you have not spoken to. A letter that threatens something the business has not decided is worse than a soft one — it is a misrepresentation in writing, and it is the sort of thing a customer keeps.